Application of GALDIT index in the Mediterranean region to assess vulnerability to sea water intrusion

Sammanfattning: GALDIT is a Vulnerability Indexing (VI) methodology that uses ranges, ratings and weights developed as a preliminary decision support tool to predict groundwater areas prone to Sea Water Intrusion (SWI). It has been only applied on porous coastal aquifers to date, in Mediterranean coastal regions, where SWI has become a growing problem. The present study tests the applicability of GALDIT VI in the Mediterranean region, by comparing the results of a porous aquifer in Akkar, Northern Lebanon to the results of a porous aquifer in Northern-East Greece. Furthermore, a feasibility of the application of GALDIT VI is done on a karstic coastal aquifer for the first time. The coastal aquifer selected for this purpose is located in Ghadir, Central Lebanon. The application of GALDIT VI on two different porous coastal aquifers shows that the theoretical ranges and ratings can always be adjusted to better fit the hydrogeological conditions of the study area. Moreover, GALDIT VI is not able to explain alone SWI evolution through time, at least not in the case of Akkar porous aquifer. Therefore, anthropogenic parameters, such as abstraction rate, should be taken into consideration. The results of the feasibility study on the karstic aquifer of Ghadir reveal the limitation of GALDIT VI in predicting sensitivity to SWI. Consequently, GALDIT VI can be fine-tuned by modifying or replacing the non-sensitive parameters/indicators by sensitive ones. The modifications include taking into account the geological structures and introducing parameters that specifically characterize karst aquifers. Finally, further investigations should be conducted to validate the solutions proposed in order to give the best possible outcome from a low resolution vulnerability assessment method as GALDIT VI.